Online deals service Groupon has shuffled its executives in a bid to jump-start overseas growth, but observers are skeptical in the face of rising competition. The changes among top-level international executives are a direct result of slowing international sales growth, says Edward Woo, an analyst with Ascendiant Capital Markets. Groupon's (GRPN) international sales growth rate slipped for the first time in Q2, says Woo, and then fell even worse